1. Field of the Invention
The present invention relates to an apparatus and a method for manufacturing golf balls and more particularly to an apparatus and the method for removing a burr from a seam of a golf ball with high accuracy and speed, so that the golf ball has great circle paths which intersect with dimples on the surface thereof.
2. Description of the Related Arts
Generally, a resin is shaped into a golf ball by a pair of semispherical molds 1A and 1B as shown in FIG. 12.
That is, a concave surface 3 having dimple-forming projections 2 is formed on each of the molds 1A and 1B. When connecting portions 4 of the molds 1A and 1B are superimposed on each other, both concave surfaces 3 form a cavity. The golf ball is shaped by pressure molding or injection molding of a resin introduce into the cavity.
As shown in FIG. 13, in a golf ball 5 formed by using the molds 1A and 1B, shown in FIG. 12 a burr 6 is formed on a portion corresponding to the connecting portions 4 of the molds 1A and 1B, namely, a seam 5a.
The burr 6 on the seam 5a is cut off the seam 5a in a subsequent process. But if dimples 8 are formed on the seam 5a, i.e., if the seam 5a is irregular, the burr 6 cannot be cut off the seam 5a. Thus, the dimples 8 cannot be formed on the seam 5a. Hence, dimple-forming projections 2 are not arranged in the vicinity of the connecting portion 4. Accordingly, with the removal of the burr 6 from the golf ball 5 manufactured by using the molds 1A and 1B, a great circle path 9 which does not intersect with the dimples 8 is formed on the seam 5a as shown in FIG. 14.
The great circle path 9 gives a bad influence on the flight performance of the golf ball and in particular on the aerodynamic symmetry. Therefore, methods for manufacturing a golf ball having no great circle path have been proposed as described below.
In a method disclosed in Examined Japanese Patent Publication No. 3-81394, convex portions 12 and concaves 13 are alternately formed on the connecting portion 11 of molds 10A and 10B as shown in FIG. 15. A seam 14a formed on a golf ball 14 is zigzagged in correspondence to the zigzagged configuration of the connecting portion 11 of molds 10A and 10B. In this manner, the great circle path is not formed on the surface of the golf ball 14.
As another method for manufacturing a golf ball having no great circle path thereon, dimples are not formed in the resin-molding process, but by a cutting process to be performed after the resin-molding process. This method is disclosed in Japanese Laid-Open Patent Publication No. 64-8983.
The above-described conventional methods are, however, inappropriate for mass-production of golf balls and incapable of manufacturing them with a high degree of accuracy. In fact, golf balls having a great circle path which does not intersect with dimples are unavailable on the market.
In the method disclosed in Examined Japanese Patent Publication No. 3-81394, it is necessary to shape the connecting portion 11 of the molds 10A and 10B into a complicated configuration. Therefore, it takes a considerable time to form the molds 10A and 10B into the above-described configuration, which increases manufacturing cost. In addition, the formation of the molds 10A and 10B leads to variations in size and configuration. Accordingly, it is difficult for the molds 10A and 10B to shape the resin into golf balls having a uniform dimension and configuration.
Normally, 280 to 540 dimples are formed on the surface of the golf ball. In the method disclosed in Japanese Laid-Open Patent Publication No. 64-8983, dimples are machined one by one. Therefore, it takes much time and labor and thus the method is inappropriate for mass-production. In addition, dimples have variations in dimensions and configurations.